Local energy generation 9
9.2 Key measures for transition to sustainable local energy systems
9.2.3 Local heat/cold production
II) Run-of-River Hydropower Plant: Roman, Romania
The project focused on the achievement of a new capacity for the production of electricity in the city of Roman and surrounding areas, for recovering renewable hydroelectricity by placing a hydropower plant on the Moldova River. Through the plant, Roman City produces its own electrical energy required to public lighting and buildings belonging to the local authority, becoming the first local administration in Romania that owns and produce electrical energy using a hydropower.
http://www.empowering-project.eu/wp-content/uploads/SV%20ROMAN/02_Roman%20SEAP.pdf
9.2.2.4 Bioenergy for electricity generation (biomass, biogas)
Combustion followed by a steam cycle is the main technology for utilizing biomass for electricity generation. Newer technological alternatives include the use of biomass in organic Rankine cycle (ORC) plants and gasification systems. Biomass is used as the main fuel but can also be co-combusted with coal or peat. Biogas from anaerobic digestion is mainly used on-site for co-generation applications while biogas can also be upgraded into biomethane towards injection into the existing natural gas grid.
Best practices for the use of bioenergy for electricity generation include biogas cogeneration based on anaerobic digestion, anaerobic digestion in the public waste recovery and treatment company, biogas cogeneration based on zootechnical wastewater and silage cereals, and biogas driven district heating networks. Other best practices include public-private partnerships between the local authority and waste management utility for anaerobic digestion of biowaste for CHP-based district heating, the recovery of methane gas from landfills to produce electricity based on gas engines, and consortiums for cogeneration plants driven by sustainable certified biomass based on waste produced locally or from local consortium companies.
9.2.3.2 Thermal energy storage (TES)
Thermal energy storage (TES) addresses the key bottleneck against the widespread and integrated use of renewable energy sources, since the renewable supply does not always coincide with demand for heating or cooling. Numerous technologies in sensible, latent or thermochemical form can time shift renewable energy supply to periods of greatest demand, each of them characterised by different specifications and specific advantages.
9.2.3.3 District Heating and Cooling (DHC)
District heating (89) and/or cooling (90) (DH/C) consists of using a centralised plant to provide thermal energy for external customers. The energy input may be supplied by fossil fuels or a biomass boiler, solar thermal collectors, a heat pump, cooling systems (thermally driven or compression chillers) or from a CHP plant. A combination of the mentioned technologies is also possible and may even be advisable depending on the technologies, the fuel used and other technical issues. The characteristics of the market and demand in the heating and cooling sectors place DH/C as a viable technological option (91).
District energy infrastructure that is based on cogeneration enables the integration of the power and thermal energy sectors so that energy can be supplied to urban energy systems more efficiently. The multiple benefits of district energy systems involve up to a 50% lower primary energy usage, related reductions in greenhouse gas emissions, and increased opportunities to integrate renewable energy sources into the heating and cooling sector (92). Urban energy infrastructure that benefits from the use of district energy systems can simultaneously contribute to reducing energy imports and provide a means to make use of residual heat sources and/or sources of free cooling, such as those provided by seawater, river, lake or aquifer water using a heat exchanger. The district heating and cooling capacity in 45 cities that are identified as champions in this field has exceeded over 36 GW and 6 GW, respectively, with about 12,000 km of district energy networks (93). In addition, district energy infrastructure can provide an opportunity for demand response and balancing in the power system when there is excess variable electricity production from renewable energy sources. For example, electricity generation from wind or solar energy can be used in large-scale heat pumps in support of the district energy infrastructure or even power-to-gas options in times of oversupply (94).
Energy efficiency benefits and advantages of DH/C are based on high SPF (Seasonal Performance Factor) due to an intensive operation of the installation, introduction of highly efficient equipment, proper insulation of the distribution network, and on efficient operation and maintenance. For example, the seasonal performance that is defined as the total amount of supplied heat over the total primary energy consumption can be improved from 0.62 for individual heat pumps to 0.85 for district heating heat pumps.
Absorption chiller seasonal performance can be improved from 0.54 for an individual absorption chiller and boiler to 0.61 for the same type of installation in a district heating network (95). Since each installation operates under different conditions, detailed engineering studies are necessary to evaluate the percentage of distribution losses in the network and overall efficiency. In addition, the use of environmentally-friendly energy resources, such as biomass or solar energy, will determine any CO2 emission reductions.
(89) SOLARGE project database contain good examples of large solar district heating. Most of them are located in Denmark and Sweden. http://www.solarge.org/index.php?id=2
(90) ECOHEATCOOL project www.euroheat.org. Supported by Intelligent Energy Europe / Danish Board for District Heating www.dbdh.dk
(91) ECOHEATCOOL: European Heating and Cooling Market Study,
https://www.euroheat.org/our-projects/ecoheatcool-european-heating-cooling-market-study/
(92) UNEP (2015) District Energy in Cities - Unlocking the Potential of Energy Efficiency and Renewable Energy, http://staging.unep.org/energy/portals/50177/DE_Executive%20Summary_lowres_double.pdf
(93) Ibid.
(94) Ibid.
(95) Y. Shimoda et al. (2008). Verification of energy efficiency of district heating and cooling system by simulation considering design and operation parameters, Building and Environment 43, pp.569-577
District energy networks thus enable a powerful solution for cities by enabling the connection of multiple thermal energy users through a piping network to environmentally optimum energy sources, such as CHP, industrial waste heat, and renewable energy sources (RES) (96). The energy and exergy savings benefit of such options in comparison to alternative heating technologies depends on the annual energy request, the population density, and the efficiency of heat production (97). Since district energy networks can better exploit existing local energy sources, such as surplus heat from electricity production and industry, the need for new thermal (condensing) capacities are effectively reduced. Similarly, District Heating (DH) can offer synergies between energy efficiency, renewable and CO2 mitigation by serving as hubs to utilize residual heat that otherwise would be wasted. DH can provide significant contributions to the reduction of both CO2
emissions and particulate matter leading to air pollution while increasing energy security.
The decarbonisation of DH/C networks requires the integration of much higher shares of RES and waste heat, the reduction of the end‐user connection costs and the development of low‐temperature heating networks. For example, cases that involve renewable energy options can be found to provide significant cost advantages among cases for district heating systems (98). In Sweden, the current focus for district heating systems is given to be renewable heat, heat recycling and their combination (99). Synergies between waste‐
to‐energy processes and district heating/cooling could also provide a secure, renewable, and in some cases, more affordable energy in displacing fossil fuels. DH/C networks can offer flexibility to the energy system by cheaply enabling the storage of thermal energy.
District Cooling (DC) can make usage of alternatives to conventional electricity cooling from a compression chiller. The resources can be natural cooling from deep sea, lakes, rivers or aquifers, conversion of surplus heat from industry, CHP, waste incineration with absorption chillers or residual cooling from re-gasification of LNG. District cooling systems can greatly contribute to avoiding electricity peak loads during summer. Table 27 compares different DC components based on the supply and distribution structure.
Table 27. Components in different district cooling systems (100) Type of District
Cooling (DC)
Components in Each Type of District Cooling Design Supply Distribution Extra Steps in the Hybrid
System Units in the
Building Conventional DC Large-scale heat
pumps/chillers Cold pipes - - Substations
for cold
Natural Cooling Natural cooling, usually from the sea or a river
Cold pipes - - Substations
for cold
Hybrid Cooling Heat Heat pipes Central
absorption heat pumps
Cold pipes Substations for cold
Sorption Cooling
(SCH) Heat Heat pipes - -
Individual sorption heat pumps
(96) IEA (2008) IEA Implementing Agreement on District Heating and Cooling, Including the Combined Heat and Power ANNEX VIII
(97) Verda, V., Guelpa, E., Kona, A., Lo Russo, S., (2012). Reduction of primary energy needs in urban areas trough optimal planning of district heating and heat pump installations, Energy 48 (1), pp. 40-46.
(98) Mikulandrić, R., Krajačić, G., Duić, N., Khavin, G., Lund, H., Vad Mathiesen, B. and Østergaard, P., 2015.
Performance analysis of a Hybrid District Heating System: A Case Study of a Small Town in Croatia, Journal of Sustainable Development of Energy, Water and Environment Systems, Vol. 3, No. 3, pp 282-302
(99) Werner S. (2017). District heating and cooling in Sweden, Energy 126 pp. 419-429
(100) AREA, 2014. Guidelines How to approach District Cooling http://area-eur.be/sites/default/files/2016- 05/Guidelines%20District%20Cooling%20140131.pdf
Large-scale district cooling systems can radically reduce the specific capacity costs (€/kW) that have to be invested when compared to individual systems per household.
The investment reduction is due to the avoidance of redundant investments and variances in customer’s peak load across time (simultaneity factor). Cities with district cooling are estimated to have a 40% reduction in total installed cooling capacity (101).
Best practices from the signatories include contract to connect municipal buildings and schools to the DH network, integrated heating systems between public buildings, initiative to increase the purchased volume of energy from the DH network, including subsidies and/or obligations for connection to DH networks, modernization and rehabilitation of DH/C networks, remote monitoring of pipelines and insulation to reduce heat losses, and installation of thermal energy distributors and thermostatic radiator valves in the DH network. The connection of low energy houses to a low-temperature DH network in Västerås, Sweden is also a promising solution.
The following box provides the best practices of Helsinki in realizing an integrated district heating and cooling system to achieve its climate obligations.
Box 39. Integrated District Heating and Cooling, Helsinki, Finland
In a country where temperatures are below 10°C for half of the year, heating buildings is a crucial basic utility. As a result, Finland has been leading in cogeneration of heat and power (also known as combined heat and power - CHP) since a long time. In Helsinki, some 93% of the buildings are connected to district heating. What may be more surprising is that the local authority has also been seriously investing in cooling solutions for its districts since a few years’ time. District cooling is now a clearly growing business in Helsinki, already covering a volume of buildings of 11.5 million m3.
Ten years ago, the local authority started a pioneering project called “Helen-IT”, which aims at cooling data centres and recovering the heat produced in this process by piping it into the district heating network, to heat buildings and provide them with hot water. This way the heat produced by the computer hall is recycled and not wasted warming up the air outside.
When the operation started, it was based on the estimation that cooling demand would grow rapidly in Helsinki despite the northern climate. The objective was to provide reliable, economical and eco-efficient cooling solutions for all types of property owners. In 2010, some 250 large buildings in the city centre were using the system, most of them being private companies.
In 2015 district cooling in Helsinki is estimated to save about 60,000 tonnes of CO2 emissions. But the advantages of “Helen-IT” are not limited to the energy savings. The solution is also totally silent and unobtrusive, as the district cooling equipment installed in the clients’ premises takes up much less space than traditional cooling devices. If all the computer halls in Finland operated on this principle, up to 500 MWh of energy could be saved every day. At the same time, a medium- sized city’s worth of buildings could be heated.
Currently there are three district cooling production methods in Helsinki, each of them adapted to the season of the year:
The absorption technique is used in the summer time when the sea water is too warm for free cooling. District cooling is produced by using thermal energy that would otherwise be lost in energy generation.
The heat pump system is used to recover thermal energy obtained from district cooling. The heat is transferred to the district heating network for heating buildings and domestic hot water.
The free cooling method produces district cooling from cold sea water between November and May, when the water temperature is below 8°C.
Pajunen, J., Integrated district heating and cooling helps Helsinki to achieve its climate obligations, http://www.covenantofmayors.eu/IMG/pdf/Helsinki_Case_Study_Covenant_Mayors_1_.pdf
(101) Possibilities with More District Cooling in Europe, ECOHEATCOOL Work Package 5, https://ec.europa.eu/energy/intelligent/projects/sites/iee-
projects/files/projects/documents/ecoheatcool_more_district_cooling_in_europe.pdf
Among other best practices, Box 40 provides the example of the district of Kirchhellen in the city of Bottrop, Germany that achieved energy self-sufficiency based on a mix of renewable energy solutions, including wind, photovoltaics, biogas, and geothermal energy, and a district heating network. Other best practices include cooperation with the local energy utility to establish a district energy network, the connection of buildings and industries to the DC network, utilization of residual heat from urban wastewater, interconnection of district heating networks and extension of distribution piping, as well as an emphasis in urban energy planning to increase the connection of buildings to the district heating network in Kristianstad, Sweden. The utilization of industrial waste heat among the signatories includes those from the local steel industry (Finspång, Sweden) and the substitution of the use of natural gas through the use of waste heat from a pulp mill (Judenburg, Austria). Targets to increase RES shares in district networks are put forth, including in Ringsted, Denmark.
Box 40. Energy Self-Sufficiency, Bottrop, Germany
Kirchhellen is the first district of the city of Bottrop with the aim of energetic self-sufficiency.
In 2009, only 4 % of the city's renewable energy consumption was produced in the district of Kirchhellen. Today, Kirchhellen produces as much energy as consumed by its' households - all from renewable sources, such as wind power, photovoltaics, biogas, and geothermal energy. To reach this aim, the local authority was able to build upon already existing structures of renewable energy production as well as on their established governance structures. Three additional wind power plants as well as the installation of a district heating network based on renewables contribute to the aim of self-sufficiency.
Furthermore, the integration of a large-scale geothermal project in domestic construction as well as plans for a zero-emission industrial area complements the integrated approach. In addition, the project "Heat Production from Effluents" contains the creation of an energy map to analyse the heat potential in effluents as well as possible heat recipients. Through the additional analysis of determining factors, such as yearly effluent temperature, or dry weather discharge, three pilot projects have been identified:
a) Heat from sewage system, b) Heat from purification plant, c) Direct usage of effluent heat.
Pilot project a) has been implemented in cooperation with the Hochschule Ruhr West which is using heat from effluents from a nearby sewer for their new building, the Energy Campus Lab. The usage of thermal energy from heat effluents contributes to the aim of the Hochschule to avoid emissions in the operation of the building.
http://www.eumayors.eu/about/covenant-community/signatories/key-actions.html?scity_id=4407 Box 41 involves the best practice of the District Heating Manual of London, which emphasizes the direction of the industry towards “fourth generation” district heating networks that is initiating to be applied in districts. In comparison to previous generations, developments towards “fourth generation” district heating networks (4GDH) addresses the integration of sectors in the energy system based on smart electricity, thermal and gas grids (102).
In smart energy systems, smart electricity grids involve generators, consumers, and those that function in both domains as prosumers to provide a sustainable, economic, and secure supply of electricity. Smart thermal grids act as an interface between centralized as well as decentralized production units and all connected facilities to satisfy heating and/or cooling demands. This includes low-temperature district heating networks that have low supply temperatures. The operation of the distribution network at lower supply temperatures reduces transfer losses and improves grid efficiency.
(102) Lund H., Werner S., Wiltshire R., Svendsen S., Thorsen J.E., Hvelplund F., Mathiesen B. V., (2014). 4th Generation District Heating (4GDH) Integrating smart thermal grids into future sustainable energy systems, Energy 68, 1-11
Box 41. District Heating Manual for London, United Kingdom
London has prepared a District Heating Manual to support the urban planning process to expand and modernize the district heating network. The main steps are put forth as:
- Mapping energy demands in the area, considering ownership and control of these demands;
- Mapping energy supplies in the area, including local heat and fuel sources;
- Mapping existing and planned district heating schemes;
- Mapping new development in the area;
- Identifying suitable locations for energy centre (s);
- Identifying routes for potential district heating networks.
In the same Manual, the direction of the industry towards “fourth generation” district heating networks (4GDH) is acknowledged.
____________________
Greater London Authority, (2013). District Heating Manual for London
Figure 2 compares the four generation of district heating developments based on energy supply, energy efficiency, and temperature level.
Figure 2. District heating generations by supply, efficiency, and temperature level
Source: Lund, H., Werner, S., Wiltshire, R., Svendsen, S., Thorsen, J. E., Hvelplund, F., Mathiesen, B.V.(102) In addition, two-way district heating involves the possibility that residual sources of heat can be shared in the network, including residual heat from data centres (103). Smart gas grids address the need for gas supplies and storage, which also have an important role in
(103) Two-way district heating creates a heat trading market for the customer
https://www.euroheat.org/news/two-way-district-heating-creates-heat-trading-market-customer/
contributing to the above grids and vice versa (104). Table 28 summarizes the progression of heat production and integration with the electricity supply towards 4GDH networks.
In such a cross-sectoral approach, there remains an important role for energy savings so that the increased penetration of variable renewable energy technologies is integrated in an optimal way. For this reason, the promotion, planning, cost, and operation of smart energy systems must be supported by a sufficient institutional framework, including analytical tools based on geographical information systems (GIS) and tariff policy (102).
Table 28. Generations of Production and System Integration in District Heating Networks